Report on Lokon-Empung (Indonesia) — October 2003
Bulletin of the Global Volcanism Network, vol. 28, no. 10 (October 2003)
Managing Editor: Edward Venzke.
Lokon-Empung (Indonesia) Small gas plume; high but variable shallow volcanic seismicity
Please cite this report as:
Global Volcanism Program, 2003. Report on Lokon-Empung (Indonesia). In: Venzke, E. (ed.), Bulletin of the Global Volcanism Network, 28:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200310-266100.
1.358°N, 124.792°E; summit elev. 1580 m
All times are local (unless otherwise noted)
The hazard status at Lokon-Empung throughout the report period of 2 June-19 October was at Alert Level 2 (on a scale of 1-4). Between 2 June and 5 October a white gas plume consistently rose 25-50 m above Tompaluan crater. The gas plume rose slightly higher, to 75 m, during the following two weeks. Seismicity remained above normal background levels during this time, with some variation (table 7). Shallow volcanic earthquakes increased in late July, but by September the weekly count was lower than in early July, eventually reaching a low the week of 15-21 September when no such events were detected. Seismicity quickly returned to high values of 138-209 shallow events per week in October.
|Date||Deep volcanic (A-type)||Shallow volcanic (B-type)||Tectonic|
|02 Jun-08 Jun 2003||13||45||20|
|09 Jun-15 Jun 2003||25||88||27|
|30 Jun-06 Jul 2003||18||81||19|
|07 Jul-13 Jul 2003||17||48||15|
|14 Jul-20 Jul 2003||9||91||19|
|21 Jul-27 Jul 2003||25||232||21|
|28 Jul-03 Aug 2003||16||157||10|
|01 Sep-07 Sep 2003||11||44||11|
|08 Sep-14 Sep 2003||7||36||20|
|15 Sep-21 Sep 2003||12||0||22|
|22 Sep-28 Sep 2003||34||22||20|
|29 Sep-05 Oct 2003||33||209||24|
|06 Oct-12 Oct 2003||5||159||14|
|13 Oct-19 Oct 2003||24||138||14|
Geologic Background. The twin volcanoes Lokon and Empung, rising about 800 m above the plain of Tondano, are among the most active volcanoes of Sulawesi. Lokon, the higher of the two peaks (whose summits are only 2 km apart), has a flat, craterless top. The morphologically younger Empung volcano to the NE has a 400-m-wide, 150-m-deep crater that erupted last in the 18th century, but all subsequent eruptions have originated from Tompaluan, a 150 x 250 m wide double crater situated in the saddle between the two peaks. Historical eruptions have primarily produced small-to-moderate ash plumes that have occasionally damaged croplands and houses, but lava-dome growth and pyroclastic flows have also occurred. A ridge extending WNW from Lokon includes Tatawiran and Tetempangan peak, 3 km away.
Information Contacts: Dali Ahmad, Hetty Triastuty, Nia Haerani, and Suswati, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).